Flame-resistant compositions of ethylene/vinyl chloride interpolymers and hydrated alumina

ABSTRACT

FLAME-RESISTANT COMPOSITIONS COMPRISING ETHYLENE/VINYL CHLORIDE INTERPOLYMER AND FINELY-DIVIDED HYDRATED ALUMINUM.

United States Patent 3,827,997 FLAME-RESISTANT COMPOSITIONS OF ETHYL-ENE/VINYL CHLORIDE INTERPOLYMERS AND HYDRATED ALUMINA Joseph G. Bergomi,In, St. Louis, Mo., assignor to Monsanto Company, St. Louis, M0.

N0 Drawing. Continuation of application Ser. No. 146,806, May 25, 1971.This application Mar. 5, 1973, Ser. No. 337,784

Int. Cl. C081 45/04 US. Cl. 26029.6 TA 10 Claims ABSTRACT OF THEDISCLOSURE Flame-resistant compositions comprising ethylene/ vinylchloride interpolymer and finely-divided hydrated alumina.

This is a continuation of the now abandoned application Ser. No.146,806, filed May 25, 1971.

This invention relates toflame resistant compositions comprisingethylene/ vinyl chloride interpolymer and finely-divided hydratedalumina.

The term nonwoven fibrous materia as used herein means a consolidatedmass of fibers laid down by mechanical, chemical, pneumatic, electricalor vacuum means, or otherwise deposited, into the desired shape, eitherfiat (webs, mats or sheets) or three-dimensional. The term E/VCl/A asused herein means ethylene/vinyl chloride/acrylamide.

The term oxygen index as used herein means the concentration of oxygenin an oxygen/nitrogen atmosphere below which combustion is not supportedand above which combustion is supported for a given substance.

The flame resistant compositions of this invention exhibit an improvedflame resistance which is totally unexpected from the teachings of theprior art. The use of finely-divided hydrated alumina as a flameresistant agent for various polymers such as styrene/butadiene/itaconicacid is well known to the art. However, the improvement in flameresistance of the S/BR as measured by oxygen index is generally limitedto about 100%. The compositions of this invention exhibit an improvedflame resistance of 300% or more as compared to the basic E/VCl/Aterpolymer.

The ethylene/ vinyl chloride interpolymers useful in the preparation ofthe flame resistant compositions of this in-' vention generally containabout to about 70 weight percent ethylene, about 30 to about 95 weightpercent vinyl chloride, and about 0.1 to about Weight percent of anadditional polar monomer component. The additional polar monomercomponent can be entirely acrylamide or a portion of the acrylamide canbe replaced by one or more polar monomers selected from the groupconsisting of acrylonitrile, methacrylamide, N-(lower alkyl) acrylamide,N-(lower alkyl) methacrylamide and N-(hydroxy substituted lower alkyl)acrylamide containing from 1 to 3 carbon atoms in the lower alkylgroups, N-[Z-(Z-methyl- 4-oxopentyl)]-acrylamide, acrylic acid,methacrylic acid, and alkali metal and ammonium salts of acrylic andmethacrylacrylic acids, maleic acid, fumaric acid, half and completealkali metal and ammonium salts of maleic and fumaric acid, aconiticacid, itaconic acid, citraconic acid, and alkali metal and ammoniumsalts thereof, acrylyl and methacrylyl esters of hydroxyalkanoic acidshaving from 2 to about 6 carbon atoms in the alkanoic acid moieties,acrylylamides and methacrylylamides of aminoalkanoic acids having from 2to about 6 carbons in the amino: alkanoic acid, hydroxyethyl andhydroxypropyl esters of acrylic, methacrylic, maleic, and fumaric acids,vinyl esters of alkanoic acids having from 1 to 6 carbon atoms such asvinyl acetate, vinyl propionate, and lower alkyl (1 "Ice to 6 carbonatoms) sulfonic acid, vinyl esters of phenylsulfonic acids, andalkylphenylsulfonic acids and acrylyl and methacrylyl esters ofhydroxyalkylsulfonic acids having from 1 to 6 carbon atoms in said alkylmoieties, and hydroxyalkylsulfonamides having from 1 to 6 carbon atomsin said hydroxyalkyl moieties. The polar monomer component generallycontains at least 50 weight percent acrylamide and preferably at leastpercent acrylamide.

Thus the interpolymers are at least terpolymers containing ethylene,vinyl chloride and acrylamide and may be a quaternary or higher polymercontaining one or more of the above exemplified additional polarmonomers in small quantities. Generally such additional polar monomerswill not be present in the interpolymer in quantities greater than about3 percent by weight.

It is preferred that the interpolymer contain from about 5 percent toabout 70 percent ethylene, 30 percent to about percent vinyl chloride,and from about 1 percent to about 5 percent acrylamide. A specificexample of choice is a terpolymer containing from about 19 to about 23percent ethylene, about 74 to about 78 percent vinyl chloride, and fromabout 2 to about 4 percent acrylamide.

The interpolymers used in accordance with this invention are generallyunmodified, but modified interpolymers are also included for use in thisinvention. The interpolymers are particularly amenable to hydrolyticmodification by the use of small quantities of a strongly alkalinematerial such as an alkali metal hydroxide, or a quaternary ammoniumhydroxide such as tetramethyl ammonium hydroxide, or by a strong acidsuch as the mineral acids, e.g., hydrochloric, sulfuric, phosphoric,nitric. The base or acid used preferably has an ionization constanthigher than 10* at 25 C.

The hydrolytic modification is carried out by treating an aqueousdispersion or polymer latex or the ethylene, vinyl chloride, andacrylamide with aqueous base or acid in an amount chemically equivalentto from about 0.1% to about percent of the amide equivalent in theinterpolymer.

Specific examples of polar monomers which can be used, as describedabove, to replace part of the acrylamide in the polar monomer componentof the interpolymer useful in this invention include acrylonitrile,N-methacrylamide, N- ethylacrylamide, N-propylacrylamide,N-hydroxymethyl acrylamide, methacrylamide, acrylic, methacrylic,maleic, fumaric, itaconic, aconitic, and citraonic acids and alkalimetal and ammonium salts of such acids, preferably the sodium, potassiumor ammonium salts, alkyl esters of such acids, e.g., methyl acrylate,ethylacrylate, butyl acrylate, methyl methacrylate, butyl methacrylate,ethyl methacrylate, monoethyl maleate, dipropyl fumarate, acrylyl 3-hydroxypropionate, methacrylyl hexamide, 2-hydroxyethyl and2-hydroxypropyl esters of acrylic, methacrylic, maleic, fumaric,itaconic, aconitic and citraconic acids, finyl formate, vinyl acetate,vinyl hexanoate, vinyl and alkyl esters of propanesulfonic acid, vinylphenylsulfonate, acrylyl and methacrylyl esters of2-hydroxypropylsulfonic acid; and N-acrylyl and N-methacrylyl2-hydroxypropanamides. I

Illustrative of interpolymers which can be used in the bonding agentcompositions for the flame retardant, bonded non-woven fibrous productsof this invention are:

ethylene/ vinyl chloride/acrylamide,

ethylene/ vinyl chloride/hydroxyethylacrylate,

ethylene vinyl chloride/acrylamide/N-isopropylacrylamide,

ethylene/ vinyl chloride/acrylamide/N-ethylmethacrylamide,

ethylene/vinyl chloride/ acrylamide/diammouium itaconate,

ethylene/vinylchride/acrylamide/monobutyl acid maleate,

ethylene/ vinyl chloride/acrylamide/N-methacrylylpropionamide,

ethylene/ vinyl chloride/acrylamide/N-methylolacrylamide, and

ethylene/ vinyl chloride/ acrylamide/ sodium methacrylate.

In general, the finely-divided hydrated alumina can be used in any sizewhich permits admixture with the ethylene/vinyl chloride interpolymers.In particular, finelydivided hydrated alumina having a particle sizefrom about 8 to about 10 microns is preferred.

The flame-resistant compositions of this invention are prepared by anymeans known to the art as, for example, mixing or milling. Theethylene/vinyl chloride interpolymers and finely-divided hydratedalumina can be admixed by hand or with conventional mixing or millingequipment. For example, admixing can be carried out with mixing rolls,dough mixers, Banbury mixers, extruders and other mixing equipment.Admixture can be carried out by adding the finely-divided hydratedalumina to a solution of the interpolymer followed by solvent removal toobtain a homogeneous flame-resistant composition. Suitable solventsinclude dimethylformamide, dimethylacetamide, pyridine and the like.Admixture can also be carried out by adding the ammonium polyphosphateto an aqueous emulsion or dispersion of the interpolymer. In manyapplications the flame-resistant interpolymer in aqueous emulsion ordispersion will be used in latex form without further treatment.

The flame-resistant compositions of this invention generally containfrom about 10 parts to about 1000 parts of weight of finely-dividedhydrated alumina for every 100 parts by weight of ethylene/vinylchloride interpolymer and preferably from about 50 to about 500 partsper each 100 parts of interpolymer.

When the flame-resistant compositions are used in the form of an aqueousdispersion, the dispersion generally contains from about 5 parts toabout 2000 parts of aqueous media by weight and from about 50 parts toabout 500 parts of finely-divided hydrated alumina by weight for each100 parts by weight of ethylene/vinyl chloride interpolymer. Suchdispersions preferably contain from about SOparts to about 1000 parts byweight of aqueous media and from about 100 parts to about 300 parts offinely-divided hydrated alumina for each 100 parts by weight ofinterpolymer for ease of application by means of dipping, soaking,spraying and the like. The preferred flame-resistant compositions ofthis invention comprise ethylene/vinyl chloride/acrylamide terpolymerscontaining to 70 weight percent ethylene, to 85% vinyl chloride and 1 to5% acrylamide, and from about 50 to about 500 parts of finely-dividedhydrated alumina.

The ethylene/vinyl chloride interpolymers useful in this invention arereadily prepared by various means well known to the art. Theinterpolymers can be prepared by first mixing ethylene and vinylchloride in an aqueous medium in the presence of any suitable anionic ornonionic emulsifier and any initiator capable of generating freeradicals in the chemical mixture at the chosen reaction temperature andpressure. The acrylamide, preferably in aqueous solution either alone ormixed with the appropriate amounts of other polar monomers, is added tothe polymerizing ethylene and vinyl chloride mixturegradually'throughout the reaction. The addition of the acrylamide ispreferably begun after about 40 to percent of the desired conversion ofthe ethylene and vinyl chloride has been reached. A shell-core latex inwhich the polar monomer is concentrated in the outer layers is produced.

The ethylene/vinyl chloride interpolymers used in this invention arepreferably prepared by a process which comprises mixing ethylene andvinyl chloride monomers in the presence of an alkaline bufferedreduction-oxidation (redox) initiator-catalyst system, water, and fromabout 1 percent to about 8 percent by weight based upon the monomerfeed, or from about 4 percent to about 7 percent based upon the polymerproduct of an anionic or nonionic emulsifying agent having ahydrophilic-lipophilic balance (HLB) value of from about 10 to about 40,and reacting the mixture at a temperature and pressure and for a timesufficient to cause polymerization between the ethylene and vinylchloride, and then to introduce acrylam'ide, either alone, or mixed withother monomers in minor amounts in an appropriate diluent such as waterinto the pressurized polymerizing reaction mixture of the ethylene andvinyl chloride. This process is described in detail in US. Pat.3,428,582 and the subject matter thereof is expressly incorporatedhereinby reference.

The following examples will illustrate this invention. Parts and percentare by weight unless otherwise indicated.

EXAMPLE 1 This example illustrates the preparatioin of a 21/ 76/ 3ethylene/vinyl chloride/acrylamide interpolymer latex.

Reaction Vessel Initial Charge H 0 to make 1700 ml. Vinyl chloride (VCl)450 Ethylene (E) 150 The above ingredients are charged to a suitablereaction vessel and heated to 30 C. with stirring to give a reactionpressure of 850 p.s.i.g. Polymerization is started by adding a 1 Msodium formaldehyde sulfoxylate- NaHSO -CH O-2H (SFS)/ 1.5 M ammoniumhydroxide (NH OH) solution to the mixture at a rate of 5.2 ml./hr. atthe same time 18 ml./hr. of a 25 percent SLS solution is added and thepressure is kept constant by the addition of pure vinyl chloride asrequired. After three hours, a 50 percent solution of acrylamide inwater solution is added at 40 ml./hr. The reaction stops after 5.5 hoursand the feed streams are turned ofi. A total of 1330 g. of VCl, ml. ofthe 50 percent acrylamide, 27 ml. of the 1 M SFS/ 1.5 M NILOH solution,and 92 ml. of the 25 percent SLS solution are added. The resultingpolymer latex is vented out the bottom of the autoclave. A total ofabout 3500 g. of the ethylene/vinyl chloride/acrylamide polymer latex isobtained containing 47 percent total solids, and 1.5 percent sodiumlauryl sulfate (based on the weight of the polymer). It has a pH of 7.7.The composition of the terpolymer is about 21/76/3 ethylene/ vinylchloride/acrylamide.

EXAMPLE 2 An aqueous dispersion of ethylene/ vinyl chloride/ acrylam-ide21 /7-6/ 3 terpolymer prepared substantially in accordance with Example1 and containing about 45 weight percent polymer solids is coagulated bymeans of tetrahydrofuran. The terpolymer is washed with water and dried.About parts of finely-divided hydrated alumina having a particle sizerange of about 8 to 10 microns are admixed with about 100 parts of thedry terpolymer to form a flame-resistant composition.

EXAMPLE 3 About 30 parts of the E/VCl/A terpolymer prepared in Example 2are dissolved in 100 parts of dimethylformamide at 25 C. with moderateagitation. To this solution is added about 10 parts of finely-dividedhydrated alumina having a particle size range of 8 to 10 microns withstirring. The solvent is removed by evaporation at reduced pressure withconstant stirring to produce a flameresistant composition.

EXAMPLE 4 An aqueous flame resistant composition comprising 100 parts ofE/VCl/A (21/7 6/3) and 300 parts of finelydivided hydrated aluminahaving a particle size range of 8 to 10 microns is prepared by admixingthe hydrated alumina with a 60 weight percent aqueous dispersion ofE/VCl/A. A film is cast in a glass plate to a dry thickness of about 4.5mils. The film is placed in a chamber having a variable oxygen/nitrogenatmosphere and is brought in contact with a small flame. The percentOxygen in the oxygen/nitrogen atmosphere is increased until it issufiicient to support combustion. The percent oxygen in theoxygen/nitrogen atmosphere at the point of combustion is termed theoxygen index. The 'E/VCl/A-hydrated alumina flame resistant film of thisExample has an oxygen index of 0.866. A control sample of the sameE/VCl/A without hydrated alumina has an oxygen index of 0.222 or justslightly above the oxygen concentration in atmospheric air.

This improvement of almost 300% in oxygen index is totally unexpectedsince hydrated alumina does not result in comparable improvements withother polymers such as styrene/butadiene/itaconic acid (57/38/5). Theoxygen index of styrene/butadiene/itaconic acid (57/ 38/ 5) is 0.173.The oxygen index of a composition comprising 1100 parts by weight ofstyrene/butadiene/itaconic acid terpolymer (57/38/5) and 300 parts ofhydrated alumina having a particle size range of 8 to 10 microns is0.330. Thus the improvement is only about 90 percent.

EXAMPLE 5 Preweighed samples of Hollingsworth and Vose nonwoven fabriccomposite comprising 75 weight percent cellulosic fiber and 25 weightpercent nylon fiber are immersed in an aqueous dispersion offlame-resistant compositions comprising an ethylene/vinyl chlorideinterpolymer and finely-divided hydrated alumina. The impregnatedfabrics are passed through a size press, Weighed, dried for about threeminutes at a temperature of about 1'1-8 C. The wet pickup offlame-resistant composition in each sample is about 270% based on theweight of the fabric. The bonded nonwoven fabrics are subjected tocalendering through a single nip for smoothness and tested for flameresistance in accordance with TAPPI-T461 vertical flammability test. Theethylene/vinyl chloride/acrylamide interpolymer contains 76 weightpercent ethylene, 2J1 weight percent vinyl chloride and 3 weight percentacrylamide and is prepared substantially in accordance with Example 1.The nonwoven fabric samples are 2.75 in. by 8.25 in. One dispersion ofethylene/ vinyl chloride interpolymer which does not containfinely-divided hydrated alumina is used as control. Results and furtherdetails are given in the Table below.

TAB LE Finelydivided hydrated Alumina in test fabric, percent byanalysis After glow, sec. Char length, in.

0 (control) Entire sheet Entire sheet consumed. consumed. 10.4 N 2.

e Based on the weight of the fiber.

butyl dicresyl phosphate, n-octyl dicresyl phosphate, isooctyl dicresylphosphate, 2-ethylhexyl dicresyl phosphate, nonyl dicresyl phosphate,decyl dicresyl phosphate, 2-npropyl-heptyl dicresyl phosphate,2-butyloctyl dicresyl phosphate, tridecyl dicresyl phosphate, tetradecyldicresyl phoshate, octadecyl dicresyl phosphate, trichloroethylphosphate and tri-(dimethylphenyl) phosphate.

The flame-resistant compositions of this invention are alsocharacterized by high tensile strength, good elongation, softness, goodhand and flexibility, good drape and resistance to many common solventsand detergents. With these properties the flame-resistant compositionsare useful as bonding agents for bonded nonwoven fibrous productssuitable for use in a wide variety of end applications including, forexample, paperboard, toweling, wrappings, wallpaper, mats napkins,tablecloths, heat or sound insulating materials, electrolyticcondensers, luggage skin and interiors, glue coated tape stocks,pressure sensitive tape stocks, projection screens, waterproof wrappingpaper, drapery headers, draperies, binders, hospital items such as caps,masks, gowns, jackets, scrub pants, capes, shoe covers, wash cloths,pillow cases, wipes, cubicle curtains, filters for food processing,motors, machines, air systems or liquid systems, electrical insulators,tapes ribbons, automobile head and arm rests, upholstery, stuifedpillows, fiberfills, sleeping bags, slip covers, bed spreads, blankets,curtains, window shades, carpeting (nonwoven), carpet backing, wearingapparel, clothing insulation, underwear, diapers, interfacing andinterliners (collars and cuffs), automotive door panels, film backingsand automotive padding.

The embodiments of this invention in which a particular property orprivilege is claimed are defined as follows:

1. Composition comprising a flame resisting amount of finely-dividedhydrated alumina and an interpolymer selected from the group consistingof .(I) an ethylene/vinyl chloride interpolymer containing from about 5to about 70 weight percent ethylene, about 30 to about Weight percentvinyl chloride, and about 0.1 to about 10 weight percent of anadditional polar component selected from the group consisting of "(A)acrylamide, and

(B) acrylamide in combination with at least one additional polar monomerselected from the group consisting of acrylonitrile, methacrylamide,N-(alkyl) acrylamide, N-(hydroxy substituted alkyl) acrylamide, andN-(alkyl) methacrylamide having from i to 3 carbon atoms in each saidalkyl group, acrylic acid, methacrylic acid and alkali metal andammonium salts of acrylic and methacrylic acid, maleic and fumaricacids, itaconic and ci-traconic acids, half alkyl esters of maleic,fumaric, itaconic, and citraconic acids having from 1 to 6 carbon atomsin said alkyl groups, acrylyl and methacrylyl esters of hydroxyalkanoicacids having from 2 to 6 carbon atoms in said alkanoic acids,acrylylamide and methacrylylamides of aminoalkanoic acids having from 2to 6 'carbon atoms in said aminoalkanoic acid, hydroxyethyl andhydroxypropyl esters of acrylic, methacrylic, maleic, and fumaric acids,vinyl esters of al'kanoic acids having from 1 to 6 carbon atoms andalkyl sulfonic acid having from 1 to 6 carbon atoms, phenylsulfonicacids, and acrylyl and methacrylyl esters of hydroxyalkylsulfonic acidhaving from 1 to 6 carbon atoms in said alkyl moieties andhydroxyalkylsulfonamides having from 1 to 6 carbon atoms in saidhydroxyalkyl moieties; and (H) interpolymers of the type described in(I) treated with an acid or a base having an ionization constant higherthan about 10- in amounts equivalent to up to about percent of the amidecontent of said interpolymer.

2. Composition of Claim 1 wherein the particle size of finely-dividedhydrated alumina is from about 8 to about 10 microns.

3. Composition of Claim 1 wherein said finely-divided hydra-ted aluminais present in amounts of from about 10 parts to about 1000 parts byweight for each 100 parts by weight of inter-polymer.

4. Composition of Claim 1 dispersed in aqueous media. I

5. Composition of Claim 1 wherein the ethylene/vinyl chlorideinter-polymer contains from about 15 to about 70 percent ethylene, fromabout 30 to about 85 percent vinyl chloride and fromabout 0.1 to about 1percent acrylamide.

6. Composition of Claim 1 wherein theethylene/vinyl chlorideinterpolymer contains from about 19 to about 23 percent ethylene, fromabout 747m about 78 percent vinyl chloride and from about 2 to about 4percent acrylamide.

7. Composition of Claim 1 wherein the interpolymer is n 8. Compositionof Claim 1 wherein the polar component of the interpolymer is acombination of acrylamide and 'N-hydroxymethylacrylamide.

9. Composition of Claim 1 together with from about 2 to about 2000 partsby Weight of aqueous media for each 100 parts by weight of interpolymerwherein the ethylene/ vinyl chloride interpoly-mer contains from about15 to about 70 percent ethylene, from about 30 to about 85 percent vinylchloride and from about 0.1 to about percent acrylamide, and thefinely-divided hydrated alumina is present in an amount from about 50parts to about 500 parts by weight'for each 100 parts by weight ofinterpolymer.

10; Composition of Claim 1 together with from about 2 to about 2000par-ts by weight of aqueous media for each 100 parts by weight ofinterpolymer wherein the ethylene/vinyl chloride interpoly-mer containsfrom about to about 85.weight percent vinyl chloride and from about 0:1to about 10 weight percent of a combination of acrylamide andN-hydroxyrnethyl acrylamide, and the finely-divided hydrated alumina ispresent in an amount from about parts to about 500 parts by Weight foreach parts by weight of interpolymer.

References Cited UNITED STATES PATENTS 3,567,491 3/197r- Graham et al.

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260- 296 TA X LUCIL-LE M. PHY'NES, Primary Examiner US. Cl. X.R.

1 17-437, 139.5 A 161; 1*6l170; 260--'29.6 M & MP, 30.6 R, 41 B, 45.7 R,78.5 B'B & T, 80.73; Digest24

